Avalanche Forecast

Issued: Feb 27th, 2019 4:08PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada swerner, Avalanche Canada

Reactive wind slabs formed in response to the recent wind event Tuesday and Wednesday. Southerly aspects will likely be more reactive to human triggers especially at treeline and above. Old, buried wind slabs still linger on on aspects and elevation

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

WEDNESDAY OVERNIGHT: Light snowfall amounts 2-5 cm with light to moderate East wind. THURSDAY: New snow 5-10 cm by the end of the day. Ridgetop winds strong from the southwest and alpine temperatures near -8. FRIDAY: Cloudy with sunny periods and isolated flurries. Ridgetop winds light from the northeast and alpine temperatures near -9. SATURDAY: Mix of sun and cloud. Ridgetop winds moderate from the East. Alpine temperatures near -16.

Avalanche Summary

On Tuesday, a skier triggered a persistent slab avalanche on an E-SE aspect between 1680-1770 m. This is believed to have failed on the early February surface hoar/ crust interface that exists 40-60 cm down. This avalanche was 100 m wide and ran 300 m in length. Wind slabs were also reactive to human triggers up to size 2 and explosive controlled wind slab avalanches were reported up to size 2.5 failing on southerly aspects 1900-2100 m. Last Sunday, a large (size 2.5) persistent slab was triggered by a skier in the Evening Ridge area. It occurred on a southeast aspect at about 2000 metres and featured a crown fracture around 50 cm deep and 350 metres wide. A weak layer from early February is suspected as the failure plane.

Snowpack Summary

Reactive wind slabs have formed on southerly slopes in response to the recent wind event. This MIN report reflects the Kootenay Pass area well. The storm last weekend brought 15-25 cm of low density snow that now covers variable old wind slabs at higher elevations and sun crusts on south-facing slopes. A weak layer of surface hoar crystals and a crust that was buried on February 7th is now 30-50 cm deep. This layer has been reactive, and has produced avalanches as large as size 3. Two other surface hoar layers are buried 50 to 80 cm deep the snowpack (referred to as the February 1st and mid-January layers) and continues to be reactive to human triggers. The mid-pack is complex and requires diligence and patience. The lower snowpack is considered generally strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Northeast winds have formed fresh and reactive wind slabs on southerly slopes and terrain features. Old, buried wind slabs also linger on a variety of aspects.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
It remains possible to trigger an avalanche on one of the surface hoar or crust layers buried 30 to 80 cm deep. These layers are most prominent around treeline elevations.
Caution around sheltered open areas at treeline and below including cutblocks, gulleys, and glades.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Use increased caution on open slopes and convex rolls at lower elevations.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 28th, 2019 2:00PM

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